Tube rolling mill



14, 19737. F, KQCKS 2,093,244

TUBE ROLLING MILL Filed Aug. 15, 1935 Patented Sept. 14,v 1937 PATENT oFFiclf.,l

TUBE ROLLING MILL Fritz Rocks, Dusseldorf, Germany Application August 5, 1933, serai N. csasss In Germany February 10, 1933 9 Claims.

The present invention relates to rolling mills and more especially -to mills for rolling thinwalled seamless tubes by stretching tubular blanks between inclined rolls.

It is an object of my invention to provide a rolling Vmill which is simple in design and economical in operation and which vdoes not strain the metal in an unsatisfactory manner.

It is another object of this invention to provide a tube rolling mill which is particularly adapted for the production of seamless tubes of small diameters, for instance tubes about 50 to 100 millimetres in diameter, and the size and weight are only a small fraction of those of the rolling mills hitherto applied to the same operation, so that the first costs of a mill according tol this invention will be far below the costs of such prior rolling mills.

The rollingv mill according to this invention is tted with inclinedvrolls, i. e., with ro1ls,vthe axes of which extend-in different planes at an angle to one another, and more than two such rolls areprovided in this mill in order to simultaneously act on more than two points of the circumference of the blanklunder operation.

Hollow blanks have already been. transformed into tubes by stretching the blank in the axial direction between more than two inclined rolls.

, However, in these mills as hitherto designed the diameters of the rolls are very small in proportion to their length, i. e., the rolls are compara-l tively thin and, in view of this, require being supported by abutments on the side averted from the blank under operation'.

In another type of rolling mills belonging to the same class the rolls are formed with annular projections or flanges designed to produce grooves in the blank in order to stretch same.

While the mills mentioned in the rst place are complicated in design and costly in construction, the latter type of mills involves the drawbeck that the annular projections forming the main operative portions of the rolls are exposed to rapid wear and at the same time subject the metal of the blank to unsatisfactory stresses.

The tube rolling mill'accor'ding to the present invention is also provided with more than-two rolls arranged to cooperate in the rolling of the same circumferential area of the blank. However here the diameters of the rolls are large as compared with their length, so that the rolls are not exposed to any undue bending stress, and

the rolls present a plain unbroken conical surunder operation are not inclined .to 'the aixisof,

the blank more than 12 in any point.

In order to form a substantially enclosed pass' and to thereby prevent the hollow blank from expanding in radial direction un/der the rolling strain, I may dispose filling pieces ola kind well known per se between adjoining rolls, the' blank being thus enclosed in a circle of rolls and filling pieces alternating with each other and`forminga drums of any dimensions, but to be quite particuylarly'useful in the manufacture of small tubes, forinstance 50 to 100 millimetres in diameter.

While the rolling mms hitherto in use for het:

rolling tubes of this kind were equipped, with rolls, the'diameter of which was the fourto sixfold of the diameter of the blank, I provide the mill with rolls having a diameter not exceeding one and one-half of the diameter of the blank, such as have hitherto been used only in connection with the rolling of materially largerY tubes. I support these rolls in pairs of bearings, one at each end, these bearings 4being adapted .to 4take up the entire rollingl pressure. Since in rolls of this kind the axial length of .the operative roll Surface does not exceed' twice the largest diameter, no inadmissible bending of the roll will arise and there is no need to provide abutments for the operative roll surface on the side averted from the blank. Since the operative roll surface is plain and devoid of all sharp-edged projections or flanges', the blank and the tube obtained from it Yare formed with a smooth surface free from projections and grooves.

In' the practical operation of my invention I prefer using rolls, the largest diameters of which do not exceed millimetres.

I yhave found it admissible and advantageous to operate a new rolling mill at the hithe'rtounheard of speed of at least 200 and preferably more than 400 revolutions per minute. By operating the mill at such high speeds a workpiece feed is obtained of 0.5 to l-.meter and even more per second, which, apart from the increase in output per unit of time, also insures uninterrupted operation and the possibility of producing tubes of far greater length and uniformity of wallthickness than was hitherto possible with mills operating at lower speeds. For lower feeding' velocity involves uneven cooling of the workpiece,

` rolling mill with inclined rolls as hitherto used Yment hitherto possible. t

i scale.

for the same purpose.

By providing a larger number of rolls I am enabled to form the rolls with an inclined rolling ,surface such that the blank can travelthrough the mill at a far higher speed than hitherto usual. Consequently the inclination of the direction of movement of the circumference of the rolls at the .point of contact with the blank relative to the axis of the blank need not exceed that is, the tangent to the surface of the rolls in the direction of their rotation is inclined to the axis of the blank by an angle not substantially less than 80.

I have found it useful to force, during the rolling operation, a lubricant into the gap between the mandrel and the blank -in order to enable the rolls to displace and shape the metal with the least possibleexpenditure of power.

In order, further, to increase the elciency of the mill by the cration of a high turning moment acting on the rolls, I have found it useful to increasethe mechanical strength of couplings,

coupling spindles, pinions etc. byhardening or tempering them, for I am thus enabled to transmit onto the rolls which may equally be hardened or tempered, twice or three times the turning mo- In the drawing aillxed to this specification and forming part thereof a rolling mill embodying my invention is illustrated diasrammcally by was In the drawing 'in elevation, while 2 is a cross'section on the line II-II in Fig. 1, and

Fig. 3 is a rside-elevation Referring to the drawing, I is the machine bed or housing and 2 are four inclined-.conical rolls, 3 being bearings supporting these rolls at either end. 4 are filling pieces, one between each pair of adjoining rolls, these pieces being mounted in the machine 'bed by means of keys I and embracing about one fourth of the circumference of each adjoining roll, their inner ends extending in close proximity of the tubular blank t mounted on a lmandrel l, which is formed with a central conduit l and a number of substantially radial branch `conduits 8, through which lubricant is forced `from a reservoir Ill under the action of a piston II. I2 are the couplings, I3 the coupling spindles and I4` is the motor driving the rolls by means of the pinions (not visible) mounted in the casing I5.

The conical faces ofthe rolls are shown to extend` at an angle of not more than 12 to the axis of the blank and to be plain and devoid of all projecting parts or grooves, the axial length of the operative roll surface being less than twice,

the largest diameter. As shown more particularly yin Fig. 2, the rolls and the iillixt,r pieces closely The couplings, coupling spindles and pinions' drawn toI a smallerare hardened or tempered, and so are the rolls themselves. v

The ratio of gearing between the driving mol I wish' it to be understood that I do not desirev to be limited to the exact details of construction shown and described for obvious modiilcations will occur to a person skilled in the art.

I` claim:-

1. In a mill .for rolling preformed tubular blanks into thin walled 'seamless tubes not substantially exceeding mm. in diameter, a stationary frame, fixed bearings mounted in said frame, and a mandrel, more than two highspeed rolls journaled in said bearings and ai'- ranged concentrically around said mandrel, and driving means adapted to drive said rolls at a speed not substantially less than about 400 R. 'P. M.; the said rolls having a diameter not substantially exceeding mm. or 1.5 times the diameter of -the blanks, the axial length of the operative surface of said rolls not. substantially exceeding twice their largest diameter.

2. In a mill for rolling preformed tubular' ssubstantially exceeding 15()` mm. or l.5 timesthe diameter of the blanks, the axlallength 'of the `operative surface of said rolls not exceeding twice their largest diameter and being inclined withrespecttotheaxisofsaid mandrelnot more than 12 at any point.

3. In a vmill for rolling preformed tubular blanksinto thin walledseamless tubes, a'stationary frame, iixed bearings mounted in said frame and a mandrel, at least four inclined high-speed rolls journaled in said bearings and arranged concentrically around said mandrel. and driving means adapted to drive said rolls at a speed not substantially less than about 400 R. P. M.; the largest diameter of said rolls not substantially exceeding 150 mm. or 1.5 times the diameter of the blank, the axial length of the operative surface of rolls not exceeding twice their largest diameter and being inclined with respect to-the axis of said mandrel not more than 12 atany point, the tangent to the surface of said rolls in the direction of their rotation being inclined to the axis of the blank by an angle not substantially less than 80.

4. In the rolling of tubular blanks into thin walled seamless tubes having diametersl not substantially exceeding 100 mm.. the process which comprises rotating the rolls of a tube mill, provided with more than two high-speed rolls Journaledin bearings fixed in a stationary frame andA arranged concentrically around a mandrel, at a speed not substantially less than about 400 R. P. M., feeding into said mill preformed blanks slidable along said mandrel at a rate not substantially less than about 0.5 meter per second and stretching said blanks -between said rollsY into thin walled tubes; the said .rolls having a diameter not substantially exceeding 150 or 1.5 times the diameter of the blanks.

5. In the rolling oi!l tubular blanks into thin walled seamless tubes having diameters not substantially exceeding mm., the process which comprises rotating the rolls of atube mill, provided with more than two high-speed rolls journaled in bearings iixed in a stationary frame and arranged concentrically around a mandrel, at a speed not substantially less than about 400 R. P. M., feeding into said mill preformed blanks slidable along said mandrel at a rate not substantially less than about 0.5v meter per second and stretching said blanks between said rolls into thin walled tubes; the said rolls having a diameter not substantially exceeding mm. or 1.5 times the diameter of the blanks, the axial length of the operative surface of saidrolls not exceeding twice their largest diameter.

6. In the rolling of tubular blanks into thin walled-seamless tubes having diameters not substantially exceeding 100 mm., the process which comprises rotating the rolls of a. tube mill, provided with at least four high-speed rolls journaled in bearings iixed in a stationary frame and arranged concentrically around a mandrel, at a speed above 400 R. P. M., feeding into said mill performed blanks slidable along said mandrel at a rate not substantially less than about 0.5 meter per second and stretching said blanks,

lbetween said rollsinto thin walled tubes, the

largest diameter of said rolls not substantially exceeding 150 mm. or 1.5 times the diameter of the blank, the axial length of the operative surface of rolls not exceeding twice their largest Adiameter and being inclined with respect to the axis of said mandrel not more than 12 at any point, the tangent to the surface of said rolls in the direction of their rotation being inclined to the axis of the blank by an angle not substantially less than 80; said rolls being positioned to draw said blanks into tubing Without other means of propelling said blanks through Asaid mill.

'7. In a mill for rolling tubular blanks into thin-Walled seamless tubes of small diameter, the combination of more than two skew rolls and guides arrangedbetween said rolls, said rolls and said-guides forming a, substantially continuous` 

